Lead bearing corrosion in locomotive engines has been one of the major concerns for original equipment manufacturers (OEMs). Total Base Number (TBN) retention has also been a technical challenge. Historically, railroad engine oils (RREO) are non-zinc containing formulations because of the silver bearings which were used in some locomotive engines. Without the benefit of zinc dialkyl dithiophosphate, the proper detergent mixture has been the key factor in control of TBN retention and lead corrosion.
In March 2008, the Environmental Protection Agency (EPA) finalized a three-part program that will dramatically reduce emissions from diesel locomotives of all types—line-haul, switch, and passenger rail. The rule will decrease particulate matter (PM) emissions from these engines by as much as 90 percent and NOx emissions by as much as 80 percent when fully implemented. This final rule sets new emission standards for existing locomotives when they are remanufactured. The rule also sets Tier 3 emission standards for newly-built locomotives, provisions for clean switch locomotives, and idle reduction requirements for new and remanufactured locomotives. Finally, the rule establishes long-term, Tier 4, standards for newly-built engines based on the application of high-efficiency catalytic after treatment technology, beginning in 2015.
Due to new EPA emission requirements and the introduction of ultra low sulfur diesel (ULSD) fuel, there will be a move to low SAPS railroad engine oils. As in heavy duty diesel oils for truck engines, there will be a decrease in TBN as well as a reduction in sulfur levels. Traditionally RREOs were 13-17 TBN oils.
The TBN will likely be lowered to 8-11 TBN due to these changes. Balancing reductions in TBN and sulfur with long standing concerns about TBN retention and lead corrosion will require a different formulation. It has been found that when TBN levels were lowered, but the components were not changed, TBN retention and lead corrosion levels suffered. A problem exists of maintaining or improving lead corrosion and TBN retention when TBN in the oils and sulfur are decreased in RREOs.
It has been discovered that formulations containing salicylate detergent in addition to the traditional components showed decreased levels of lead corrosion and better BN retention.
1. Prior Art
Research Disclosure No. RD0493012 teaches the use of salicylate detergents and supplementary antioxidants for improved lead corrosion in low sulfated ash, phosphorus and sulfur heavy-duty diesel formulations.
Tomomi et al, JP 3925978 teaches a composition which comprises lubricating base oil, (a) perbasic alkali earth metal salicylate, (b) perbasic alkali earth metal phenate and (c) bis-type alkenyl succinimide, bis-type alkyl succinimide or their boron adducts.
Locke, EP 1256619 teaches a lubricating oil composition comprising (A) an oil of lubricating viscosity, in a major amount, and added thereto, (B) a detergent composition comprising one or more metal detergents which comprises metal salts of organic acids, in a minor amount, wherein the detergent composition comprises more than 50 mole % of a metal salt of an aromatic carboxylic acid, based on the moles of the metal salts of organic acids in the detergent composition, and (C) one or more co-additives, in a minor amount; wherein the total amounts of phosphorus and sulfur derived from (B) or (C) or both (B) and (C) are less than 0.1 mass % of phosphorus and at most 0.5 mass % of sulfur, based on the mass of the oil composition.
Shaw, U.S. Published Patent Application 2006/0052254 teaches an oil composition, which contains a salicylate, having sulfur (up to 0.3 wt %), phosphorus (up to 0.08 wt %), sulfated ash (up to 0.80 wt %), comprises a mixture of an oil of lubricating viscosity (a); and an overbased alkali or alkaline earth metal alkyl salicylate lubricating oil detergent (b) having salicylate soap (20-25 wt %).
Reiff, U.S. Pat. No. 2,197,832 teaches a mineral oil composition which incorporates a small quantity of a multifunctional compound selected from that group of class of metalorganic compounds which is referred to as the oil-soluble or oil-miscible metal salts of alkyl-substituted hydroxyaromatic carboxylic acids.
Yagishita, U.S. Pat. No. 7,563,751 teaches a lubricating oil composition comprising a base oil having a sulfur content adjusted to 0.1 wt % or less, and at least one of two different alkali or alkali earth metal salicylate mixtures.
Yasushi, Japanese Patent No., JP 2007217607 teaches a diesel engine oil which contains mineral oil and/or synthetic oil as base oil, salicylate type cleaning agent (1-8 mass %) and diphenylamine derivative (0.005-0.03 mass %) as additive.